Mobile Site ›

Print Page Email Page
Print Friendly View

Test ID: FQPPS
Porphyrins, Feces

Useful For Suggests clinical disorders or settings where the test may be helpful

Evaluation of persons who present with signs or symptoms suggestive of porphyria cutanea tarda, hereditary coproporphyria, variegate porphyria, congenital erythropoietic porphyria, or erythropoietic protoporphyria

Genetics Test Information Provides information that may help with selection of the correct test or proper submission of the test request

Specimen submitted must contain at least 100 g of feces. The laboratory may not be able to provide interpretable results for small specimens.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

The porphyrias are a diverse group of disorders caused by defects in the biosynthesis of heme and characterized by accumulations of porphyrinogens, porphyrins, and their precursors in plasma, red blood cells, tissues, urine, and feces.

 

Fecal porphyrin excretion becomes increased during clinical expression of congenital erythropoietic porphyria, porphyria cutanea tarda, hereditary coproporphyria (HCP), and variegate porphyria (VP), the porphyrias that commonly present with bullous skin lesions. However, in quiescent phases of VP or HCP, as well as prior to puberty, fecal porphyrin excretion may be within normal limits. Other cutaneous porphyrias, such as erythropoietic protoporphyria, may also have increased fecal porphyrin excretion.

 

Fecal porphyrins analysis, together with erythrocyte porphobilinogen deaminase analysis, is necessary to distinguish among acute intermittent porphyria (AIP), HCP and VP.

 

Separate quantitation of the porphyrin isomers improves the diagnostic sensitivity because the different forms of porphyria have distinctive profiles (see Interpretation).

 

See Porphyria (Acute) Testing Algorithm and "Porphyria (Cutaneous) Testing Algorithm in Special Instructions. Refer to The Challenges of Testing For and Diagnosing Porphyrias, Mayo Medical Laboratories Communique 2002 Nov;27(11) for more information regarding diagnostic strategy.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Porphyrins

mcg/24 hours

Uroporphyrin I

<120

Uroporphyrin III

<50

Heptacarboxyl Porphyrin I

<40

Heptacarboxyl Porphyrin III

<40

Isoheptacarboxyl Porphyrins

<30

Hexacarboxyl Porphyrin I

<10

Hexacarboxyl Porphyrin III

<10

Isohexacarboxyl Porphyrins

<10

Pentacarboxyl Porphyrin I

<20

Pentacarboxyl Porphyrin III

<20

Isopentacarboxyl Porphyrins

<80

Coproporphyrin I

<500

Coproporphyrin III

<400

Isocoproporphyrins

<200

Protoporphyrins

<1,500

Coproporphyrin III/Coproporphyrin I Ratio

<1.20

See The Heme Biosynthetic Pathway in Special Instructions.

Interpretation Provides information to assist in interpretation of the test results

Porphyria    

Biochemical Abnormalities

Congenital
erythropoietic
porphyria

Increased series I isomers, especially coproporphyrin I

Porphyria
cutanea tarda

Increased heptacarboxyl porphyrin III and isocoproporphyrins, usually accompanied by increased isohexacarboxyl and isopentacarboxyl porphyrins

Hereditary
coproporphyria

Increased coproporphyrin III, and coproporphyrin I to a lesser extent

Increased coproporphyrin III
to coproporphyrin I ratio
(usually >10.0)

Variegate
porphyria

Increased coproporphyrin III and protoporphyrin; coproporphyrin I and isocoproporphyrins may be increased to a lesser extent

Increased coproporphyrin III to coproporphyrin I ratio (a lesser degree than found in HCP, <10.0)

Increased protoporphyrin typically to a greater extent then the coproporphyrins

Erythropoietic
protoporphyria

Typically increased protoporphyrin, but may be normal

Acute intermittent
porphyria

Typically normal, but during acute phase may see increases in uroporphyrin I and uroporphyrin III 

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Heme from red meat can contribute to fecal protoporphyrin via action of intestinal microbes and cause a misleading indication of erythropoietic protoporphyria or variegate porphyria.

 

Specimen submitted must contain at least 100 g of feces. The laboratory may not be able to provide interpretable results for small specimens.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. Anderson KE, Sassa S, Bishop DF, et al: Disorders of heme biosynthesis: X-linked sideroblastic anemia and the porphyrias. In The Metabolic Basis of Inherited Disease. 8th edition. Edited by CR Scriver, AL Beaudet, WS Sly, et al. New York, McGraw-Hill Medical Publishing Division, 2001; pp 2991-3062

2. Sassa S: The hematologic aspects of porphyrias. In Williams Hematology. 7th edition. Edited by MA Lichtman, E Beutler, K Kaushansky, TJ Kipps U Seligsohn, J Prchal. New York, McGraw-Hill 2005, Ch 57

3. Elder GH: The differentiation of porphyria cutanea tarda symptomatica from other types of porphyria by the measurement of isocoproporphyrin in feces. J Clin Pathol 1975;28:601-607

Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test